Thickness Mediated Morphology Evolution in Sub-10-nm Metal Film Deposition: Implications for Nondestructive Testing

Thickness in sub-10-nmmetal film deposition is a seldom exploredparameter that can influence not only the film mechanical propertiesbut also the surface functional characteristics. In this study, wedesigned bilayer systems comprising Au on a poly(dimethylsiloxane)(PDMS) substrate to reveal a unique thickness-mediated surface morphologyevaluation phenomenon. Our results show that, within a specific rangeof elastic modulus of the selected PDMS substrate, surface wrinklingstarts when the deposited theoretical Au thickness is around 0.2 nm,reaches a maximum deformation at thickness 1-2 nm, and disappearswhen the thickness is equal to or larger than 8 nm. The thickness-mediatedwrinkling on and off suggest that film thickness can strongly impactthe patterns observed on soft elastomers. This finding indicates thatwhat we observed may not be the intrinsic surface properties but ratherthickness-controlled wrinkling. Using 2 nm Au deposition as a highlysensitive nondestructive testing method, a potential application foridentifying surface defects on solid surfaces is proposed.